message count

Counts incoming messages over a specified time interval and outputs a message containing the count result.

Configuration

Count parameters

• Interval in seconds: Time interval in seconds for counting messages. The node will output the message count at each interval and reset the counter.
• Output time series key prefix: Prefix used to create the property name in the output message that holds the count result. The property name will be formatted as {prefix}_{serviceId}, where serviceId is the unique identifier of the ThingsBoard service instance (e.g., “tb-rule-engine1”).

JSON Schema

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{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "TbMsgCountNodeConfiguration",
  "type": "object",
  "properties": {
    "interval": {
      "type": "integer",
      "description": "Time interval in seconds for counting messages"
    },
    "telemetryPrefix": {
      "type": "string",
      "description": "Prefix for the output telemetry key"
    }
  },
  "additionalProperties": false
}

Message processing algorithm

1. Initialize counter: On node initialization, creates a counter set to 0 and schedules the first tick message based on the configured interval.
2. Process incoming message:
   • Regular message: Increments the message counter by 1 and acknowledges the message
   • Tick message: Processes the accumulated count and generates telemetry output
3. Generate telemetry output (on tick):
   • Places the current message count in the message data under the key {telemetryPrefix}_{serviceId}
   • Resets the message counter to 0 for the next interval
   • Adds metadata with delta key containing the actual time difference since last scheduled tick
   • Creates a POST_TELEMETRY_REQUEST message with tenant as originator
4. Schedule next tick:
   • Calculates the next tick timestamp to maintain consistent intervals
   • Schedules the next internal tick message with appropriate delay

Output connections

• Success
  • Generated result message containing the message count for the interval

Examples

Example 1 — Basic message counting

Incoming messages over 5 seconds

• Message 1 at t = 0s
• Message 2 at t = 1s
• Message 3 at t = 3s

Node configuration

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{
  "interval": 5,
  "telemetryPrefix": "msgCount"
}

State of the system

Current service ID is tb-rule-engine1.

Outgoing message at t = 5s

Type: POST_TELEMETRY_REQUEST

Originator: current tenant

Data:

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{
  "msgCount_tb-rule-engine1": 3
}

Metadata:

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{
  "delta": "5000"
}

Result

After 5 seconds, a result message is generated showing that 3 messages were processed during the interval. The counter is reset to 0 for the next interval.